Abstract: A process for fabricating a substrate having a dielectrically isolated region, using energy beam recrystallization. An island of polysilicon is formed on an insulating substrate and a cap containing a dopant is coated on the entire surface of the substrate. A laser beam is irradiated through the cap, and the polysilicon is recrystallized to form a doped first single crystal silicon layer. A second single crystal silicon layer is grown over the first single crystal layer. The first single crystal layer is used as a buried layer, and a semiconductor device is fabricated in the second single crystal layer. This process avoids the existence of crystal imperfections at the boundaries of the single crystal layers.